feat(admin): 优化用户权限分级·统一头像·数据分析面板修复

- fix(DataAnalysisPanel): 活跃用户卡片固定 400px + overflow-y 独立滚动容器，底部渐变遮罩提示滚动；列表项 tooltip 增加 max-height 与 overflow 截断；新增圆形头像显示与 @error 回退首字母
- feat(admin): 新增 getUserAvatarUrl 统一头像策略链（OAuth identity→Gravatar→DiceBear 7.x initials），stats/realtime、active-users、users/index 三处接口返回 avatarUrl
- fix(admin): 建立 SUPER_ADMIN(100)>ADMIN(80)>USER(10) 分级常量与 canChangeRoleOf/canResetPasswordFor 等谓词；reset-password、[id].put、index.post 全面应用级别守卫；前端 UserManager 按钮按权限禁用、availableRoles 按操作者级别过滤 SUPER_ADMIN/ADMIN 等高角色

server/api/admin/users/index.get.ts

@@ -96,26 +96,36 @@ export default defineEventHandler(async (event) => {
         meowNickname: true,
         meowBoundAt: true,
         createdAt: true,
-        updatedAt: true
+        updatedAt: true,
+        avatarProvider: true,
+        avatarProviderUserId: true,
+        email: true
       },
       with: {
-        identities: {
-          columns: {
-            provider: true,
-            providerUsername: true
-          },
-          where: (identities, { eq }) => eq(identities.provider, 'github')
-        }
+        identities: true
       }
     })
 
-    // 处理用户列表，添加头像字段
-    const formattedUsers = usersList.map((user) => ({
-      ...user,
-      avatar: user.identities?.[0]?.providerUsername
-        ? `https://github.com/${user.identities[0].providerUsername}.png`
-        : null
-    }))
+    const { getUserAvatarUrl } = await import('../../../utils/user-avatar')
+
+    const formattedUsers = usersList.map((user) => {
+      const avatarUrl = getUserAvatarUrl(
+        {
+          id: user.id,
+          name: user.name,
+          username: user.username,
+          email: user.email,
+          avatarProvider: user.avatarProvider,
+          avatarProviderUserId: user.avatarProviderUserId
+        },
+        user.identities || []
+      )
+      return {
+        ...user,
+        avatar: avatarUrl,
+        avatarUrl
+      }
+    })
 
     // 计算分页信息
     const totalPages = Math.ceil(total / limitNum)